> throughout history

Ancient egypt? Roman times? Medieval times? Byzantine times? Pre-colonial Philippines? Pre-colonial America?

I think it may have started in the late 1800s at the earliest. I would need a bit more evidence to be convinced that your model of individual to nuclear to extended etc has been a thing longer than a few centuries, vs the vast majority of human life experience being in nomadic hunter-gathering, villages, farmland, and walled city-states. We just had clans which were all our family. A fellow villager wasn't much different than a cousin. The individual and nuclear family, not so much a thing.

There's extensive written evidence as far back as writing goes of recognizable family units. Here[1] we see a young man in 18th century B.C.E writing to his mother to ask for new clothing for school. It refers to household units with mothers and fathers having discrete roles. In 1250 B.C.E.[2] Egyptian workers took days off to take care of their wives, or sick members of their immediate household. Cross cultural examples abound. In Mexica (Aztec) culture adult life began upon marriage where a couple was given a small house and plot of land.

[1] https://en.wikipedia.org/wiki/Letter_from_Iddin-Sin_to_Zinu

[2] https://mymodernmet.com/ancient-egyptians-attendance-record/

I think I'd need quite a lot of evidence that families weren't the major unit of society. A hunter-gatherer tribe is an extended family, so that only proves the point. If there's more than about 30 people in one then surely family based factions will form within it to some extent.

Probably you're focusing too much on the parent comment's mention of nuclear family. Even that, despite only being named a few decades ago, is likely to exist to some extent. Even in some ancient tribe or village, most people would favour their spouse (or equivalent) or child over a cousin or niece/nephew if some dispute formed. That hardly seems controversial.

> the vast majority of human life experience being in nomadic hunter-gathering, villages, farmland, and walled city-states.

in which they lived in families, extended families and tribes as the primary units. I didn't understand your argument at all.

It was _especially_ like this further back. You literally could not survive without the tribe, and the tribe had norms-and-values you had to adhere to, some of which were to do with family units. This went for nomads and settlers alike.

The Odyssey is in theaters right now; it rather famously deals with the importance of family and that's a close to 3000 year old poem.